Stamping

Sheet metal stamping is the main manufacturing method used to produce chassis and body components in the automotive industry. It is also used for many other applications, including domestic appliances, building and construction and aerospace industries. Therefore stamping is an important process for the Australian and International manufacturing industry. In the automotive industry, the demands for shorter lead times, higher strength sheet materials, reduced lubrication in the press shop and the increased use of manufacturing process simulation for virtual engineering, has led to research in many areas.

The main focus of Deakin University's Stamping Research group is on the following areas:

The understanding, prediction and alleviation of tool wear using:

advanced numerical tools and analytical methods to better understanding the contact, sliding, deformation and temperature conditions that are critical to the wear process.

detailed experimental characterisation and analysis of tool wear mechanisms and tool life under laboratory and industrial conditions.

thermal-mechanical-metallurgical modelling for predicting final part properties, phase fractions and hardness during the stamping, quenching and cooling processes.

predicting the crash properties of the stamped components, with the aim of designing components with local tailored mechanical properties to improve crash performance and structural efficiency.

Research Projects

Tool wear analysis for sheet metal stamping tools

In the automotive industry, the demands for reduced weight and increased safety have led to the increased the use of advanced high strength steels (AHSS). These steels offer significant advantages in weight reduction and improved crash performance. However, the higher strength causes a number of manufacturing problems, due to the higher forming loads required. These problems include tool wear and galling, which involves pick-up (galling) of the sheet material on the tools and subsequent scratching of the sheet surface. Tool wear can increase the manufacturing costs substantially and lead to significant quality issues, which can require the use of capital intensive tooling material solutions to alleviate the problem (PDF-273kb).

Numerical simulation of galling in sheet metal forming

The increasing application of Advanced High Strength Steel (AHSS) in the automotive industry to fulfil crash requirements has introduced higher levels of wear in stamping dies and parts. It has been seen in sheet metal forming that some materials tend to stick to the tool surface. The transferred material will increase friction at the tool surface and therefore increase the required forming force. The adhered material that has become hard due to work hardening cause more material from the work piece to be removed and adhered to the new formed asperity, making bigger lumps of material on the tool surface. These unevenly distributed lumps deteriorate the surface quality of the formed part in the form of severe scratches along the material sliding direction (PDF-150kb).

By increasing the level of environmental and safety standards, the demand for fuel efficient and higher strength vehicles is increasing accordingly. One approach to improve fuel efficiency is to reduce the weight of vehicles, while maintaining high strength structures to protect passengers against crashes.

The hot stamping process has been one of the innovative technologies resulting in very high-strength components by heating the sheet metal up to the austenitization temperature (900-950°C), then forming and quenching the sheet metal in a water cooled die faster than a critical cooling rate (27-30°C/s) which causes the hardest steel phase (Martensite) to appear in the microstructure. Such high strength components are beneficial in anti-intrusion zones of the vehicle structure. In some vehicle parts e.g. B-Pillar, the requirements from different zones are different. A slower cooling rate is necessary to achieve softer steel phases and higher ductility (PDF-230kb).

Car bodies are now stamped from significantly higher strength sheet steels, to reduce vehicle mass and emissions in service. Consequently, stamping dies are now subjected to more severe forming forces and contact stresses, resulting in increased tool wear-related problems and significant losses in manufacturing efficiency. Therefore it is a main concern to monitor the conditions of tools continuously, in order to avoid sudden breakdowns, production of faulty parts and reduction in efficiency and quality. This will require extracting signal of interest out of observed signals.

'Blind' signal separation (BSS) techniques are commonly used to address the problems with similar nature in communications systems, biomedical applications and mechanical system. BSS techniques aim to recover unobserved (source) signals from observed mixtures and 'Blind' refers to the unavailability of knowledge about original sources and the transmission or mixing system (PDF-256kb).